Caption: View of the tunnel of the "main ring" accelerator at Fermilab, Illinois. The main ring is 2 kilometres in diameter & contains two accelerators, one on top of the other. The top accelerator, which employs ordinary magnets (red & blue), accelerates protons up to 150 GeV. It then passes them to the lower accelerator, which has superconducting magnets (yellow), & which is designed to accelerate the protons up to 1000 GeV. 1000 GeV is 1 TeV, and hence the lower accelerator is known as the Tevatron. (1982)